fix #3609: cifs: add support to SMB 3.11

fix #3609: cifs: add support to SMB 3.11

Added support for the SMB version SMB3_11 When the `min protocol =
SMB3_11` in the smb.conf, the CIFS mount will return with the
following error:
```
CIFS VFS: cifs_mount failed w/return code = -95
```
added an optional option to use the `vers=3.11`

Signed-off-by: Moayad Almalat <m.almalat@proxmox.com>
Tested-by: Fabian Ebner <f.ebner@proxmox.com>
[ Thomas: move text from cover letter to commit message &
  add S-o-b ]
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>